Fluid operated contractile drive

ABSTRACT

A fluid operated contractile drive which has a contractile hose ( 4 ) extending between two head pieces ( 2  and  3 ), and attached to at least one head piece ( 2  and  3 ) by having its respective end section ( 10 ) clamped in an annular clamping gap ( 26 ) defined between clamping surfaces ( 24  and  25 ), extending in an at least partially inclined manner in relation to the longitudinal axis ( 9 ) of the contractile hose ( 4 ) of a first clamping unit ( 22 ) having a force output means ( 17 ) serving for external force output and a second clamping unit ( 23 ) able to be shifted axially in relation to the first clamping unit. In addition to the contractile hose ( 4 ) between the two clamping unit ( 22  and  23 ) there are loading means ( 45 ), effective between same, such loading means ( 45 ) acting on the clamping unit ( 22  and  23 ) to produce a reduction of the width of the clamping gap ( 26 ).

This application claims priority based on an International Applicationfiled under the Patent Cooperation Treaty, PCT/EP03/01781, filed on Feb.21, 2003, and German Patent Application No. DE 202 05 719.4, filed onApr. 11, 2002.

FIELD OF THE INVENTION

The invention relates to a fluid operated contractile drive comprising acontractile hose extending between two head pieces, and contractinglongitudinally when its internal hose space defined by it is acted uponby fluid pressure to exert axial tension forces on the head piecesdrawing them together, the contractile hose being attached to at leastone head piece by having its respective end section clamped in anannular clamping gap defined between clamping surfaces, extending atleast partially inclined in relation to the longitudinal axis of thecontractile hose and of a first clamping unit having a force outputmeans serving for external force output and a second clamping unit ableto be shifted axially in relation to the first clamping unit.

BACKGROUND OF THE INVENTION

In the case of a known contractile drive disclosed in the German patentpublication 10,034,389 A1 a contractile hose extends between two headpieces which are respectively provided with two clamping units and whichare screwed together like a gland nut. Between the clamping units anannular clamping gap is defined, in which the contractile hose isclamped at its associated end region. If the internal space of thecontractile hose is charged with a pressure medium subject to a certainactuating pressure, the contractile hose will expand radially and willsimultaneously pull the two head pieces toward one another. It is inthis manner that it is possible for external structures or,respectively, components, which are fixed on the force output means ofthe head pieces, to be moved relatively toward each other and/or clampedtogether.

In the case of the known contractile drive there was the problem thatowing to its liability to deformation the contractile hose could bepulled out of the clamping gap. Therefore the two clamping units weredesigned to be adjusted in the longitudinal direction of the contractiledrive and the tightening faces were so contrived that owing tofrictional effects between them and the contractile hose a certainentraining effect is produced with the result that on actuation of thecontractile hose there is an automatic reinforcement of the gripping orclamping action between the two clamping units.

It has however now been discovered that there are still certainshortcomings with the known clamping attachment, which are moreparticularly significant at raised temperatures or in the case of theuse of relatively soft hose materials. The material then tends to creepand in the worst case the contractile hose may slip out of the headpiece completely.

SUMMARY OF THE INVENTION

Accordingly one object of the present invention is to provide acontractile drive of the type initially mentioned with a furtherimprovement of the connection between the contractile hose and one orboth of the two head pieces.

The design for achieving this object is characterized by loading meansprovided in addition to the contractile hose and effective between thetwo clamping units and acting on the clamping units to reduce the widthof the clamping gap.

It is in this manner that it is possible to ensure that the end section,placed in the clamping gap, of the contractile hose will always remainfirmly clamped reliably, even if owing to fatigue of the hose materialor for some other reason there is a tendency to creep, which wouldinherently reduce the clamping action. Owing to the loading means thetwo clamping units are automatically reset to a degree dependent on thereduction in the wall thickness of the clamped end section of thecontractile hose so that the desired clamping action may be permanentlymaintained even despite the effect of unfavorable environmentalconditions.

In principle it would be possible to so design the loading means thatthey only take effect following or at the occurrence of certain events,for example when the temperature of the surroundings has exceeded acertain value. Such a design could be realized by the use of so-calledmemory metal. The simplest and at least presently most economic designis one in which the loading means are so designed that they are alwaysin action. This is something which may be more particularly achieved bythe use of loading means having resiliently elastic properties, moreespecially in the form of a structure corresponding to a mechanicalspring means. Particularly compact dimensions may in this case beproduced by having mechanical spring means, which comprises a bellevillewasher stack.

Furthermore structures of the design are possible in the case of whichthe action of the loading means is produced, or at least aided, by thefluid pressure medium employed for the operation of the contractiledrive. For this purpose an actuating space may be provided betweenaxially opposite actuating faces of the two clamping units, such spacebeing constantly connected with the inner space of the hose. Theclamping action produced will in this case be dependent directly on thepressure action on the contractile drive so that the clamping actionincreases with an increase in the load on the contractile drive.

In the case of a preferred embodiment of the invention the clampingfaces so run together at an angle within the clamping gap that theirdistance from the longitudinal axis of the contractile hose increasestoward the outer end region, axially opposite to the contractile hose,of the respective head piece. The diameter of the annular clamping gapthen preferably increases toward the outer end region of the head piece.

It has been found to be particularly advantageous if at least one of theclamping faces is designed with a corrugated cross sectional outline. Itis then a question here preferably of that clamping face which acts onthe contractile hose at the inner periphery.

Preferably the respective head piece is provided with holding meansserving to load the two clamping units to maintain a basic clampingeffect on the contractile hose irrespectively of the fluid actuatingeffect in the inner space of the hose. The holding means may for examplebe in the form of a screw connection, which is provided between aclamping nut and the force output part of the first clamping unit.

A particularly compact arrangement is produced if the loading meansresponsible for the active clamping effect of the contractile hose arelocated in a region which is within the contractile hose.

In connection with the design in accordance with the inventionfurthermore an advantageous safety feature may be produced. Since owingto the reliable fixation and automatic resetting of the clampingattachment slipping of the contractile hose out of the head piece isprevented, when there is an increase in overloading here will be theeffect such that the hose material in the clamped region, which becomesthinner, will become slightly porous. Air may escape through the fineholes so that overloading of the hose material or even splitting thereofis avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described with reference to theaccompanying drawing in detail.

The single FIGURE thereof shows a preferred embodiment of the inventionin the form of an actuating means, partly in longitudinal section.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The contractile drive illustrated comprises the two (first and second)spaced apart head pieces 2 and 3, only one head piece 2 beingillustrated completely in order to make the drawing morestraightforward.

The two head pieces 2 and 3 are connected with each other by way of acontractile hose 4. At least in the non-activated state of thecontractile drive the contractile hose 4 possesses a cylindrical tubularconfiguration. The longitudinal axis of the contractile drive, which atthe same time represents the longitudinal axis of the contractile hose4, is indicated at 9.

The contractile hose 4 possesses an elongated hose body 5 preferablymanufactured of a material having rubber-like properties. As a materialuse is preferably made of rubber or an elastomeric material havingsimilar properties. A strand structure 1, only indicated in the drawingin chained lines, is embedded in the material of the hose body 5 andsuch structure is preferably completely surrounded by the hose bodymaterial and possesses an arrangement which is coaxial to the hose body5. The structural form of the contractile hose 4 can more particularlybe as disclosed in the German patent publication 29,906,626 (utilitymodel) or in the European patent publication 0 161 750 B1.

The contractile hose 4 has its two axial end sections 10 so fixed at theassociated head pieces 2 and 3 that on the one hand there is afluid-tight connection between the hose body 5 and the respective headpiece 2 and 4 and on the other hand the stand structure 1 is in aposition of exerting tension forces on the respective head piece 2 and3. Instead of the strand structure 1 other suitable means could beemployed to transmit the axial tension forces.

The contractile hose 4 delimits an internal hose space 13, which at theend is terminated by the two head pieces 2 and 3. Into the space 13 inthe hose there opens at least one fluid duct 14, that in the workingexample extends preferably coaxially right through the first head piece2 shown in its entirety. The fluid duct 14 is able to be connected witha fluid line, not illustrated in detail, which leads to a source ofpressure medium. By the use of an intermediately placed control valvearrangement there is the possibility of feeding a fluid pressure mediuminto the inner space 13 of the hose or of letting off such medium fromit. Preferably the contractile drive is operated with gaseous pressuremedium, more especially compressed air. It is also readily suitable foroperation using a hydraulic fluid for example oil or water.

Each head piece 2 and 3 is provided with force output means 17 at aposition accessible from the outside. Such means are in the workingexample constituted by a threaded section of the respective head piece 2and 3 and render possible an attachment of the respective head piece 2and 3 to some component, not illustrated in detail. For instance itwould be possible to use the force output means 17 of the first headpiece 2 to join it to the frame of a machine and to connect the otherhead piece 3 with a machine part moved in relation to the machine frame.The contractile drive is suitable for practically all applications, inwhich two components are to be shifted in relation to one another or tobe clamped.

The connection with the corresponding component may be directly by wayof the force output means or with the interposition of an adapter part,not illustrated in detail, which is fixed to the force output means 17.

For activation of the contractile drive by way of the fluid duct 14pressure medium at the predetermined operational pressure is fed intothe interior 13 of the hose. Owing to such gage pressure the wall of thecontractile hose 4 is thrust radially outward so that there is an actionin the form of a radial widening of the contractile hose 4. Theconsequence of this is that the contractile hose 4 is simultaneouslyacted upon to perform an axial contraction, axial tension forcesproduced by the contractile hose 4 causing an opposite movement togetherof the head pieces 2 and 3. This in turn means that the components heldby the force output means 17 of the head pieces 2 and 3 are acted on tomove together. Dependent on the particular circumstances this isaccompanied by a greater or lesser opposite movement together of the twohead pieces 2 and 3, the displacement of the head pieces 2 and 3 inrelation to each other being termed the stroke.

For deactivation of the contractile drive the pressure medium is atleast partly let off from the interior space 13 of the hose. Thecontractile hose 4 then contracts back to its original length so thatthe head pieces 2 and 3 return to the original position. This returnmovement may if necessary be aided by additional measures, as forexample using return springs.

The particular movement and deformation properties of the contractilehose 4 are ensured in the working example by the strand structure 1. Thestructure involved here is for example as described in the said Germanpatent publication 29,906,626 (utility model) or in the European patentpublication 0 161 750 B1. Preferably the strand structure 1 comprises aplurality of bendable strands, which have a high degree of flexibilityand simultaneously a high tensile strength in the form of one or morefibers, a type being preferred, in which the strands extend helicallyand peripherally around the hose body 5 between the head pieces 2 and 3and more particularly are arranged crossing over so that rhombic gridregions are formed. Owing to the action of the internal pressure in thecontractile hose 4 a change of the rhomb angle is caused, somethingwhich ultimately means that axial tension forces are established in thestrand structure at the end sections 10 of the contractile hose, suchforces being transmitted to the head pieces 2 and 3.

The force transmission to the head pieces 2 and 3 is possible becausethe contractile hose 4 is firmly held in place at its end sections 10 inthe respectively associated head piece 2 and 3. For this purpose thehead pieces 2 and 3 are provided with a particularly advantageousclamping device 18, which is preferably identically provided in the caseof both head pieces. However, there is also the possibility of onlyproviding one such clamping device 18.

The clamping device 18 is a direct component of the respective headpiece 2 and 3. It comprises a first clamping unit 22, which is providedwith the force output means 17 and furthermore possesses a secondclamping unit 23 separate from the first clamping unit 22, such secondunit not having any force output means 17.

The two clamping units 22 and 23 fit coaxially into one another, a firsttightening face 24 provided on the first clamping unit 22 being placedradially opposite to a second tightening face 25 on the second clampingunit 23. The two tightening faces 24 and 25 being are orientated athwartthe longitudinal axis 9 and facing each other.

Between the two clamping faces 24 and 25 the two clamping units 22 and23 define an annular clamping gap 26. Such gap is open toward the innerend side, facing the respectively other head piece, the contractile hose4 having its end section 10 concentrically fitting into the clamping gap26 from the open end.

The two clamping units 22 and 23 are so firmly clamped together onassembly of the contractile drive that they exert a clamping force(termed the basic force) on the wall of the end section 10, lyingbetween them. The clamping faces 24 and 25 then contact on the one handthe inner face and on the other hand contact the outer face of the hosebody 5, against which they are firmly braced.

The end section 10 of the contractile hose 4 is externally surrounded bythe first clamping unit 22. The second clamping unit 23 extends from theend face coaxially into the contractile hose 4.

The second clamping unit 23 is in the working example constituted by aconical element, whose enveloping face constituting the second clampingface 25 has, for part of the length and preferably for the entirelength, a configuration tapering conically toward the contractile hose4. However, the second clamping face 25 preferably is not smooth butcorrugated in cross section in its outline. As a result there is anouter face with an axial sequence of alternating annular hills andvalleys.

The first clamping unit 22 is multi-part in design and possesses a forceoutput part 28 provided with the force output part 17 and furthermore atightening nut 29 designed in the form of a gland nut. The force outputpart 28 has an axially extending, central bearing tailpiece 32 fittinginto a complementary bearing recess 33 in the second clamping unit 23,such bearing recess 33 preferably being constituted by a stepped accessopening 34 extending through the full length of the second clamping unit23. The force output part 28 also possesses an axial through hole 35,which together with length section, adjoining the bearing tailpiece 32,of the through opening 34 constitutes the fluid duct 14 and is providedwith the force output means 17 as a female screw thread.

The two clamping units 22 and 23 are designed to move in relation toeach other in the longitudinal direction of the contractile hose 4, thepossible direction 36 of motion being indicated by a double arrow. Herethe bearing recess 33 together with the bearing tailpiece 33 surroundingit constitute an axial slide guide.

The tightening nut 29 has a sleeve-like structure with a first clampingsection 42 defining the inwardly directed first tightening face 24 andan attachment section 43 axially adjoining it, which externally extendsover the force output part 28 at a flange-like section. Between thetightening nut 29 and the force output part 28 there are holding means44, which define a screw connection rendering possible a variation ofthe relative axial position of the two components. Instead of the screwconnection other holding means with the same function could be selected.

The first tightening face 24 provided on the tightening nut 29 has thesame slope as the second tightening face 25 turned toward it. Itpreferably has a smooth surface or only a slight degree of roughness.

In the case of both tightening faces 24 and 25 the obliqueness is suchthat the distance from the longitudinal axis 9 becomes larger on gettingcloser to the outer end region, axially opposite to the contractile hose4, of the head piece 2. The diameter of the annular clamping gap 26consequently becomes greater from the inner end of the head piece 2axially outward.

The clamping device 18 additionally comprises, besides the componentsdescribed so far, loading means 45 effective between the two clampingunits 22 and 23, which loading means are in a position of acting on thetwo clamping units 22 and 23 to reduce the width B of the clamping gap26. In the working embodiment the loading means 45 have resilientlyelastic properties and are constituted by a mechanical spring means,which is arranged coaxially between the second clamping unit 23 and theforce output part 28 of the clamping unit 22.

Preferably the loading means 45 comprises a belleville washer.

For the sake of having a compact and space-saving structure the loadingmeans 45 are in the working example in a region located within thecontractile hose 4. They are seated in a actuating space 46, which isplaced to the fore of the bearing tailpiece 32 toward the secondclamping unit 23, it being defined by a widened section of the throughopening 34.

The actuating space 26 is delimited by two axially opposite actuatingfaces 47 and 48 of which the first actuating face 47 is provided on theend face of the bearing tailpiece 32 and the second actuating face 48 isopposite to it on the second clamping unit 23. Radially to the outsidethe actuating space 46 is directly delimited by the second clamping unit23, which fits over the bearing tailpiece 32 like a gland sleeve.

The loading means 45 acted simultaneously on the two actuating faces 47and 48 and so thrust the second clamping unit 23 away from the forceoutput part 28 causing the second tightening face 25 to move toward thefirst tightening face 24.

By way of the through opening 34 the actuating space 46 is furthermoreconstantly connected with the interior 13 of the hose.

During assembly of the contractile drive firstly after previousinsertion of the loading means 45 the second clamping unit 23 is slippedonto the bearing tailpiece 32 of the force output part 28. No tighteningnut 29 is fitted in this case. Then the end section 10 of thecontractile hose 4 is plugged on as far as engagement with an abutment52 onto the second clamping unit 23. The contractile hose is then flaredout like a trumpet. After this the tightening nut 29 previously slippedonto the contractile hose 4 is pushed over the unit comprising the forceoutput part 28 and the second clamping unit 23 so that the secondclamping unit 23 assumes a position coaxially within the tightening orloading nut 29. The tightening nut 29 is now screwed on the force outputpart 28, the first tightening face 24 thrusting from the outside againstthe contractile hose 4, which bears internally against tightening face25. The supporting force of the second tightening face in this case isdue to the loading means 45, which bear against the two clamping units22 and 23, between which they are placed.

The tightening nut 29 is tightened until the desired basic clampingaction of the contractile hose 4 is achieved. During this operation thesecond clamping unit 22 is slipped coaxially over the bearing tailpiece32 and simultaneously the intermediately arranged loading means 45 arecompressed so that a return force is built up, which is constantlyeffective and supplies the opposite force for the clamping in positionof the contractile hose 4.

Previously performed empirical measurements serve to ensure that thedesired basic clamping action is reached when the tightening nut 29 hasbeen screwed to a certain extent on the force output part 28.

The contractile hose 4 is now anchored in the clamping gap 26, the hosematerial being deformed in accordance with the configuration of thetightening faces 24 and 25.

If during operation of the contractile drive creep of the material ofthe hose body should occur the loading means 45 will prevent a reductionin the holding force with the preselected basic clamping action. Anyreduction in the wall thickness of the contractile hose 4 within theclamping gap 26 will be immediately and automatically compensated forbecause the second tightening face 25 is caused to follow up by theforce of the loading means 45. The clamping gap will be closed somewhat,but the clamping forces are maintained. Even un unfavorable conditionsthis means that the contractile hose 4 will be prevented for slippingout of the head pieces 2 and 3.

As an alternative to the constantly acting loading means 45 a designwould be possible in which the action of the loading means would onlybegin when a certain event takes place, as for instance when aparticular temperature is reached. This would more particularly allowthe use of memory-metal with the properties of assuming particularconfigurations in a manner dependent on temperature.

In the working embodiment there is a further effect. This effectinvolves the use of a supporting fluid force for the effect of theloading means 45 on the basis of the fact that the fluid pressureobtaining in the interior space 13 of the hose simultaneously acts inthe actuating space 46 as well and has a tendency to thrust the twoactuating faces 47 and 48 away from each other.

A seal 53 placed between the two clamping units 22 and 23 and preferablybetween the bearing tailpiece 32 and the second clamping unit 23prevents pressure medium from escaping between the relatively movableparts and into the surroundings.

Departing from a design, in which only friction forces between the headpiece and the contractile hose serve to cause a reduction in the size ofthe clamping gap, the installation of separate loading means 45 inaddition to the contractile hose 4 offers the advantage of high efficacyunder all operational states even in the case of changes in theproperties of the material of the hose body 5.

Owing to the clamping device 18 a secure hold of the contractile hose 4is achieved, even if the wall thickness is substantially reduced owingto deformation of the material. The fact that even in the case of asubstantial reduction in the thickness of the wall bursting of thecontractile hose is not to be feared is dependent on the fact that fineholes are produced in the thin hose material creeping out of theclamping gap 26, such holes permitting an escape of fluid under gagepressure. It is in this manner that the design in accordance with theinvention takes a certain safety aspect into account as well.

1. A fluid operated contractile drive comprising a contractile hoseextending between two head pieces, and contracting longitudinally whenits internal hose space defined by it is acted upon by fluid pressure toexert axial tension forces on the head pieces drawing them together, thecontractile hose being attached to at least one head piece by having itsrespective end section clamped in an annular clamping gap definedbetween clamping surfaces, extending at least partially inclined inrelation to a longitudinal axis of the contractile hose, of a firstclamping unit having a force output means serving for external forceoutput and a second clamping unit able to be shifted axially in relationto the first clamping unit, and further comprising loading meansprovided in addition to the contractile hose and effective between thetwo clamping units and acting on the clamping units to reduce the widthof the clamping gap, and wherein the contractile hose comprises a hosebody of a material with rubber elastic properties and a strand structurearranged coaxially to the hose body, the strand structure being embeddedin the material of the hose body.
 2. The contractile drive as set forthin claim 1, wherein the loading means are so designed that they areconstantly effective.
 3. The contractile drive as set forth in claim 1,wherein the loading means possess resiliently elastic properties.
 4. Thecontractile drive as set forth in claim 1, wherein the loading meanscomprise a mechanical spring means.
 5. The contractile drive as setforth in claim 1, wherein, between mutually oppositely placed actuatingfaces of the two clamping units, an actuating space is defined, whichcontains the loading means.
 6. The contractile drive as set forth inclaim 5, wherein an actuating space is connected with the interior ofthe hose for fluid transfer.
 7. The contractile drive as set forth inclaim 1, wherein the clamping surfaces are at such a slope within theclamping gap that their distance from the longitudinal axis of thecontractile drive increases toward the outer region, axially opposite tothe contractile hose of the head piece.
 8. The contractile drive as setforth in claim 1, wherein one or both of the clamping surfaces have aconical configuration at least partially over approximately their entirelength.
 9. The contractile drive as set forth in claim 1, wherein atleast one of the clamping surfaces possesses a corrugated crosssectional outline.
 10. The contractile drive as set forth in claim 1,wherein the first clamping unit fitted with the force output means fitsaround the contractile hose on the outside thereof.
 11. The contractiledrive as set forth in claim 1, further comprising holding means servingto brace together the two clamping units in order to maintain a basicclamping action of the contractile hose independently of the state offluid actuation of the interior of the hose.
 12. The contractile driveas set forth in claim 1, wherein the first clamping unit comprises aforce output part, provided with the force output means, and atightening nut able to be screwed on the force output part and havingone of the tightening faces, the second clamping unit having the othertightening face being arranged coaxially within the tightening nut andbeing borne in an axially sliding fashion on the force output part. 13.The contractile drive as set forth in claim 12, wherein the secondclamping unit fits externally around the bearing tailpiece of the forceoutput part for axial sliding motion.
 14. The contractile drive as setforth in claim 12, wherein the loading means are arranged between thesecond clamping unit and the force output part.
 15. The contractiledrive as set forth in claim 1, wherein the loading means are located ina region, which is within the contractile hose.